A medical image diagnostic technique using an X-ray diagnostic apparatus, an MRI apparatus, an X-ray CT apparatus, or the like has rapidly progressed with advances in computer technology, and become indispensable to today's medical care.
Recently, X-ray diagnosis has advanced mainly in the field of circulatory organs with improvements in catheter techniques. For example, in general, an X-ray image diagnostic apparatus for diagnosis of circulatory organs moves an imaging unit including an X-ray generation unit, an X-ray detector, and a C-arm which supports them, thereby allowing imaging of an object placed on a top from an optimum angle. Furthermore, the X-ray image diagnostic apparatus moves the X-ray detector close to an imaging portion of the object, thereby allowing imaging from an optimum position.
Since the imaging unit is moved near the object, it may be brought into contact with the object. To avoid this problem, there is known a method of avoiding damage or injury due to contact or the like by stopping the movement of the moving portion when the imaging unit is brought into contact with the top, a patient, or the like, by detecting the speed of the moving portion, the current and/or power to a driving means, the position of the moving portion, and the like.
In a technique disclosed in patent literature 1, for example, the external dimensions of an object placed on a top are calculated using three-dimensional image data of the object acquired by X-ray fluoroscopy from a plurality of angles, and an interference avoidance region corresponding to the outline of the object is set based on the calculated dimensions. When an imaging unit enters the set interference avoidance region, the moving speed of the imaging unit is decelerated.
In conventional interference control described above, interference points are set in portions (portions of interest) of the X-ray diagnostic apparatus, with which interference (contact) readily occurs, the three-dimensional positions (XYZ coordinates) of the interference points are calculated in consideration of the positions (angles and distances) of respective movable axes, and the clearance between each interference point and an interference (contact) target object (for example, a still object or moving object) is calculated. Before interference (contact) actually occurs, a warning sound is generated and a warning is displayed to indicate that interference will occur, and a corresponding axial operation is decelerated/stopped.
In conventional interference control, processing of calculating the coordinates of each interference point and processing of calculating the distance between the interference point and a target object are performed for each processing loop of the firmware of the X-ray diagnostic apparatus. Therefore, the clearance between the target object and each interference point at given time is compared with a predetermined threshold to perform determination, and the interference operation is controlled based on the result. The space coordinates of each interference point are generated and updated based on the latest position information and angle information of each movable axis during control processing every time the processing loop is executed.
In such conventional interference control, since control is not executed in consideration of the moving direction (operating direction of each movable axis) and moving speed (operating speed of each movable axis) of each interference point, it is impossible to detect the acceleration when the plurality of movable axes simultaneously operate or noninterference (the axes pass each other but are not brought into contact with each other) when the movable axes operate parallelly. Therefore, in conventional interference control, it is difficult to suppress the more precise interference operation in consideration of the operating speed and operating direction of each movable axis.